Backside metallization depositions/coatings can be applied to the semiconductor chips or other microelectronic devices via sputtering, evaporation, electroplating, electroless plating etc. which are deposition technologies that are known to those familiar with the art. There are a variety of reasons metallizations are placed on the backside of the semiconductor substrate in the semiconductor industry. They can be used on integrated circuits to help dissipate heat build-up during operation of the device. They can also be used to modify the electrical properties of the semiconductor substrate. They can also be used to increase the mechanical strength or reliability of a thinned substrate following a backgrind process.
Backside metallization layer(s) are generally placed on the backside of thinly ground or full thickness chips/devices while the chips/devices are still in wafer form.
Backside metallization requires suitable adhesion between the semiconductor substrate material and the initial backside metallization layer. Subsequent metal layers can then be applied dependent on the intended application provided the added metal depositions/coatings have a suitable level of adhesion between layers for long term reliability.
Copper and its alloys are highly used backside metallization layers due to their high electrical conductivity and thermal heat transfer. However, Cu and its alloys can become corroded or oxidized in subsequent processing steps, during assembly, and/or when subjected to high humidity environments.
A corroded or oxidized backside metal surface presents a variety of problems which could include but are not limited to: a discolored backside surface that will interfere with automated assembly vision requirements (especially if a laser marking is present), increased risk of extended corrosion shortening the life of the part, increased risk of extended corrosion inhibiting the overall performance of the device.
One known solution is to apply an outer corrosion resistant metallization layer of gold, platinum, silver, platinum or palladium. However, the cost of each of these metals is prohibitively high. Therefore a more cost-effective solution is needed.